What Pollutants Are Measured in the Air? - Aerosols

Aerosols are tiny particles that are suspended in the air all around us. Although some aerosols are large enough to be visible to the naked human eye, the majority are so small that we do not even notice them. However, they have the ability to reflect, absorb and scatter light from the sun, which allows them to influence the earth’s temperature and energy budget both directly and indirectly.

This occurs in a direct sense when the sun’s rays are either reflected or absorbed directly by the particle in question. If the former occurs, the aerosols can have a cooling effect on the surrounding environment; if the latter takes place, they can contribute to global warming. Indirectly, aerosols contribute to the formation of clouds, which affect weather patterns and reduce the temperature directly beneath them.

Where do aerosols come from?

Aerosols can occur in the atmosphere through natural or manmade processes. One of the principal causes of natural aerosols is volcanic ash. When sulphur dioxide is spewed into the environment after a volcanic eruption, it reaches the stratosphere and is converted into sulphuric acid, where it remains for a period of around two years. During this time, it will reflect the sun’s rays and create a cooling effect on the troposphere and the Earth’s surface.

Another naturally occurring cause of aerosols is desert dust. Although these particles of sand are normally too dense to float in the air, they can be blown across great distances and up to heights of 15,000m or more by strong gusts of wind. Unlike volcanic SO2, these particles absorb sunlight and can result in a warming effect on their surrounding environs.

Finally, humans have also contributed significant volumes of aerosols to the atmosphere since the Industrial Revolution. They can be formed through the destruction of forested areas, but they are primarily created through the combustion of coal and oil, forming sulphate aerosols. These persist in the atmosphere for a matter of days but reflect sunlight in that time, contributing to the cooling effect.

What are the effects of aerosols?

Aside from the climatic effects of aerosol concentrations outlined above, they have also been known to adversely impact human health. This is especially noticeable in those who suffer from respiratory ailments such as asthma, since the inhalation of aerosols can restrict their airwaves and cause difficulties with breathing.

However, the slow movement and relative stability of aerosols makes them a much more reliable atmospheric tracer for climate scientists than other contaminants or gases which are susceptible to chemical reactions. By monitoring the emissions, concentrations and movements of aerosols, researchers can learn valuable information about the exchange of air between the stratosphere and the troposphere, atmospheric behaviour in the polar regions and the transportation of contaminants like dust, smoke and volcanic ash.

The upcoming virtual CEM conference this March is set to take a deep dive into all things emissions-related, so interested parties are invited to attend and expand their knowledge on the subject.